Disposable single unit-dose syringe with locking plunger



Nov. 18, 1969 I. SOLOWEY 3,478,937

DISPOSABLE SINGLE UNIT-DOSE SYRINGE WITH LOCKING PLUNGER Filed Jan. 22, 1968 i W k INVENTOR. 2 4-" [0/6 fazazug l/ 42;

United States Patent US. Cl. 222386 2 Claims ABSTRACT OF THE DISCLOSURE A single use syringe including a barrel with slidable plunger therein, the plunger being not returnable outwardly after being once depressed.

This invention relates generally t9 syringes such as are used to administer medication into the body cavity (other than by oral means) via a parenteral administration unit.

It is generally well known to those skilled in the art, that a proper amount of medication administered is an important element in the treatment of a patient. With a conventional syringe such as is presently widely used, an inexperienced technician, often in effecting a withdrawal of the instrument, accidentally pulls back the plunger, thus withdrawing also a portion of the medication already instilled. This is of course seriously objectionable and in want of improvement.

Accordingly it is a principal object of the present invention to provide an improved syringe; wherein the plunger is locked against returning after it has been depressed.

Another object is to provide an imp oved syringe that is accordingly adaptable for onetime use thereby assuring against being refilled with an inferior medication.

Yet another object is to provide an improved syringe for one time use which accordingly would contain a unit dose quantity of medication to assure administration of a correct amount thereof.

Other objects are to provide a disposable unit-dose syringe with locking plunger which is simple in design, inexpensive to manufacture, rugged in construction, easy to use and etficient in operation.

These and other objects will be readily apparent upon a study of the following specification and the accompanying drawing wherein:

FIGURE 1 is a side elevation view of the present invention shown partly in cross section, and illustrating the device in an initial position prior to use,

FIGURE 2 is a similar view shown fragmentarily, and showing the device during a plunging operation,

FIGURE 3 is a view similar to FIGURE 1 showing the plunger fully depressed and unable to be returned toward the initial position,

FIGURE 4 is a fragmentary side view of a modified form of the invention,

FIGURE 5 is a similar view thereof in an alternate position.

Reference now to the drawing in detail, the reference numeral .10 represents a disposable single unit dose syringe with locking plunger according to the present invention, wherein there is a barrel 11 and a plunger 12.

The barrel 11 made preferably of glass comprises a cylindrical member having a constricted neck 13 and outlet opening 14 at one end thereof. At its opposite end 15, a wide opening is provided for receiving a plunger head 16. The cylindrical side wall 17 of the barrel encloses a central chamber 18 wherein a single dose unit of medication 19 is stored adjacent the plunger head.

3,478,937. Patented Nov. 18, 1969 In the present invention, a collar 20 made of rigid material such as non-flexing plastic is rigidly affixed over the end 15 after the plunger head has been assembled into the barrel. The collar 20 has an inwardly extending flange 21 having a central opening 22.

The plunger 12 comprises a stern 23 secured at one end to the plunger head, the stem extending outwardly of the barrel and having an enlarged knob 24 at its other end. Intermediate the ends of the stem a collar unit 25 is rigidly secured around the plunger stem, the collar unit 25 comprising a non-flexing ring 26 and a disc 27 made of flexible material such as soft rubber or flexible plastic. The ring 26 has a circular, outer edge 28 which is slightly less in diameter than the opening 22 so to permit movement therethrough. The edge 28 may be downwardly tapered inwardly so to assure against the ring becoming hung up in abutment with the collar 20. The disc is adjacent the outer side of the ring and has an edge 29 of diameter greater than the opening 22 whereby it must be distorted when moved therethrough.

In operative use, to administer the medication, the plunger is moved as indicated by the arrow 30 in FIGURE 2. When the collar unit 25 reaches the barrel collar 20, the ring 26 passes therethrough 'without engagement therewith, but the disc being larger in diameter must be fixed as shown in the figure so as to squeeze past. Immediately after the disc has passed therethrough it straightens to its flat original position and at the same instant the plunger has traveled its full stroke into the barrel. The medication thus being fully administered, the device is removed from the patient. Should now force be accident-ally applied to pull the plunger outwardly, the disc will abut against the underside of the collar 20 preventing outward movement of the plunger. It will be noted that the ring adjacent the inner side of the disc will prevent flexing of the latter, whereas flexing was unobstructed in the opposite direction.

In FIGURES 4 and 5, a modified form 40 of the invention is shown wherein the above described barrel collar 20 and collar unit 25 are substituted by a mechanical device which comprises a pair of pawls 41 each secured pivot-ally free at one end on a pin 42 mounted in tandem relation on the stem 43. A notch 44 is provided on opposite sides of the stem for the purpose of receiving the pawls completely flush within the general cylindrical contour of the stem, whereby the stem may slide freely downward through an opening 45 in a rigid collar 46 wherein accordingly the opening 45 may not be distorted. A compression coil spring 47 extending through a transverse extending opening 48 bears at its opposite ends against the pawls and normally urges them apart. Upon downward movement of the plunger, the pawls are pivoted into the notches by force of the edge of rigid collar 46. After passing through the collar, the pawls immediately again spring into outward position to prevent upward movement of the plunger again.

While various changes may be made in the detail construction, it is understood that such changes will be within the spirit and scope of the present invention.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A disposable single unit dose syringe comprising a barrel containing the medication to be administered and a plunger head mounted snugly for axial movement in the barrel, said plunger head having an actuating rod of smaller diameter extending through one end of the barrel, including a locking means mounted on the rod at a predetermined fixed distance from the plunger head, in further combination with a collar mounted on the end of the "barrel encompassing the rod, said collar having a central hole through which the rod passes, said locking means coacting with said collar to permit axial movement of said plunger head to a predetermined position in said barrel, wherein the locking means comprises a relatively inflexible member of smaller dimension than the collar hole and a relatively flexible portion larger than the hole extending radially beyond the inflexible member 'whereby said member can pass through the hole with said flexible portion flexibly engaging the collar to snap behind the collar when the plunger has been moved to the determined position.

2. A syringe as in claim 1 wherein the member is frusto conical and located between the plunger head and the 15 flexible portion.

References Cited UNITED STATES PATENTS 1,798,116 3/1931 'Brockway 128218 2,015,970 10/1935 Schoene 128-218 2,661,126 12/1953 Spencer 222-386 FOREIGN PATENTS 1,149,735 12/1957 France.

449,762 9/1927 Germany.

ROBERT B. REEVES, Primary Examiner H. S. LANE, Assistant Examiner US. Cl. X.R. 12-8-218 

